Role of platelet-activating factor in pathogenesis of acute pancreatitis

Investigation of the involvement of platelet-activating factor in the control of hypertension by aerobic training. A randomized controlled trial

Although studies have demonstrated the effectiveness of exercise in controlling systemic arterial hypertension (SAH), the mechanisms involved in this effect are still poorly understood. Thus, this study investigated the impact of aerobic training on the relationship between platelet-activating factor (PAF) circulating levels and blood pressure in hypertensives. Seventy-seven hypertensive subjects were enrolled in this randomized controlled trial (age 66.51 ± 7.53 years, body mass 76.17 ± 14.19 kg). Participants were randomized to two groups: the intervention group (IG, n = 36), composed of hypertensive individuals submitted to an aerobic training protocol, and the control group (CG, n = 41), composed of non-exercised hypertensives. Body mass index, arterial blood pressure, quality of life, respiratory muscle strength, and functional capacity were assessed before and after 12 weeks. PAF and plasma cytokine levels were also evaluated respectively by liquid chromatography coupled with mass spectrometry and enzyme-linked immunosorbent assay. Aerobic training promoted a significant reduction in blood pressure while functional capacity, expiratory muscle strength, and quality of life, PAFC16:0 and PAFC18:1 plasma levels were increased in comparison to the CG (p < 0.05). In addition, multiple correlation analysis indicated a positive correlation [F (3.19) = 6.322; p = 0.001; R2adjusted = 0.499] between PAFC16:0 levels and expiratory muscle strength after aerobic training. Taken together, our findings indicate that PAF may be involved in the indirect mechanisms that control SAH, being mainly associated with increased respiratory muscle strength in hypertensive subjects undergoing aerobic training.

Trends and recent developments in pharmacotherapy of acute pancreatitis

Acute pancreatitis (AP), a complex inflammatory disease of the pancreas, is associated with increased morbidity and mortality. Currently, no specific therapies are approved for its treatment, and management is primarily based on supportive care. Despite enhanced understanding of AP pathogenesis, patients remain at significant risk owing to a lack of targeted drug treatments. Therefore, there is an urgent need for effective pharmacological therapeutic measures which may inhibit the early systemic inflammation, thereby preventing subsequent organ failure. This narrative review summarizes the available treatment options for AP and highlights the potential drug classes and pharmacologic therapies including those under clinical development. Although, several therapies targeting different aspects of AP pathogenesis have been investigated, some therapies with promising preclinical activity have been rendered ineffective in clinical trials. Other novel drug classes or molecules including dabigatran (anticoagulant), ulinastatin (protease inhibitor), infliximab (monoclonal antibody), spautin-A41 (autophagy inhibitor), and CM4620-Injectible Emulsion (calcium channel inhibitor) await further clinical assessment. Alternative treatment options using stem cells and nanoparticles are also being explored and may hold promise for AP therapy. However, challenges for exploring targeted treatment approaches include disease complexity, timing of therapeutic intervention, and establishing appropriate clinical endpoints. Understanding the role of specific biomarkers may help in identifying appropriate targets for drug discovery and facilitate determining relevant clinical study endpoints to monitor disease severity and progression, thereby aiding in design of more precise therapies with improved clinical outcomes.

Therapeutic effect of rupatadine against l-arginine-induced acute pancreatitis in rats: role of inflammation

Acute pancreatitis (AP) is an abrupt inflammatory disorder causing high morbidity and mortality. As AP is an insidious medical emergency, a curative modality is required instead of a preventive measure. Thus, we investigated the possible curative effect of rupatadine on a rat model of AP. Rupatadine is a potent histamine receptor 1 (H1R) and platelet-activating factor (PAF) blocker. We used four groups of six Wistar rats as follows: the control group received vehicle; the rupatadine control group received rupatadine as 6 mg/kg orally; the AP group received l-arginine intraperitoneally, and the treatment group received rupatadine at 1, 6, and 24 h after l-arginine injection. The levels of serum amylase, pancreatic oxidative parameters, and pancreatic cytokines were measured. PAF, histamine, and myeloperoxidase levels were determined in the pancreas. Histopathological and immunohistochemical examinations were performed to determine nuclear factor kappa-B (NF-κB) and caspase 3 expressions. Oxidative damage and severe inflammation were detected in the pancreas of the AP group. Rupatadine reduced the oxidative damage and the levels of proinflammatory cytokines, PAF, histamine, myeloperoxidase, NF-κB, and caspase 3 expressions. It restored the pancreatic acini to almost normal condition. Rupatadine induced important anti-inflammatory and antiapoptotic effects against l-arginine-induced AP.

Protective Effects of Natural Polysaccharides on Intestinal Barrier Injury: A Review

Owing to their minimal side effects and effective protection from oxidative stress, inflammation, and malignant growth, natural polysaccharides (NPs) are a potential adjuvant therapy for several diseases caused by intestinal barrier injury (IBI). More studies are accumulating on the protective effects of NPs with respect to IBI, but the underlying mechanisms remain unclear. Thus, this review aims to represent current studies that investigate the protective effects of NPs on IBI by directly maintaining intestinal epithelial barrier integrity (inhibiting oxidative stress, regulating inflammatory cytokine expression, and increasing tight junction protein expression) and indirectly regulating intestinal immunity and microbiota. Furthermore, the mechanisms underlying IBI development are briefly introduced, and the structure-activity relationships of polysaccharides with intestinal barrier protection effects are discussed. Potential developments and challenges associated with NPs exhibiting protective effects against IBI have also been highlighted to guide the application of NPs in the treatment of intestinal diseases caused by IBI.

Efficacy of Early Percutaneous Catheter Drainage in Acute Pancreatitis of Varying Severity Associated With Sterile Acute Inflammatory Pancreatic Fluid Collection

OBJECTIVE

The aim of the study was to evaluate the efficacy of early percutaneous catheter drainage (PCD) for sterile acute inflammatory pancreatic fluid collection (AIPFC) in acute pancreatitis (AP) of varying severity.

METHODS

Retrospective analyses were performed based on the presence of sterile AIPFC and different AP severities according to 2012 Revised Atlanta Classification.

RESULTS

Early PCD contributed to obvious decreases in operation rate (OR, P = 0.006), infection rate (IR, P = 0.020), and mortality (P = 0.009) in severe AP (SAP). In moderate SAP with sterile AIPFCs, however, early PCD was associated with increased OR (P = 0.009) and IR (P = 0.040). Subgroup analysis revealed that early PCD led to remarkable decreases in OR for patients with persistent organ failure (OF) within 3 days (P = 0.024 for single OF, P = 0.039 for multiple OF) and in mortality for patients with multiple OF (P = 0.041 for OF within 3 days and P = 0.055 for 3-14 days). Moreover, lower mortality was found in SAP patients with early PCD-induced infections than with spontaneous infections (P = 0.027).

CONCLUSIONS

Early PCD may improve the prognosis of SAP with drainable sterile AIPFCs by reducing the OR, IR, and mortality.

Forty Years Since the Structural Elucidation of Platelet-Activating Factor (PAF): Historical, Current, and Future Research Perspectives

In the late 1960s, Barbaro and Zvaifler described a substance that caused antigen induced histamine release from rabbit platelets producing antibodies in passive cutaneous anaphylaxis. Henson described a ‘soluble factor’ released from leukocytes that induced vasoactive amine release in platelets. Later observations by Siraganuan and Osler observed the existence of a diluted substance that had the capacity to cause platelet activation. In 1972, the term platelet-activating factor (PAF) was coined by Benveniste, Henson, and Cochrane. The structure of PAF was later elucidated by Demopoulos, Pinckard, and Hanahan in 1979. These studies introduced the research world to PAF, which is now recognised as a potent phospholipid mediator. Since its introduction to the literature, research on PAF has grown due to interest in its vital cell signalling functions and more sinisterly its role as a pro-inflammatory molecule in several chronic diseases including cardiovascular disease and cancer. As it is forty years since the structural elucidation of PAF, the aim of this review is to provide a historical account of the discovery of PAF and to provide a general overview of current and future perspectives on PAF research in physiology and pathophysiology.

Organ Failure Due to Systemic Injury in Acute Pancreatitis

Acute pancreatitis may be associated with both local and systemic complications. Systemic injury manifests in the form of organ failure, which is seen in approximately 20% of all cases of acute pancreatitis and defines "severe acute pancreatitis." Organ failure typically develops early in the course of acute pancreatitis, but also may develop later due to infected pancreatic necrosis-induced sepsis. Organ failure is the most important determinant of outcome in acute pancreatitis. We review here the current understanding of the risk factors, pathophysiology, timing, impact on outcome, and therapy of organ failure in acute pancreatitis. As we discuss the pathophysiology of severe systemic injury, the distinctions between markers and mediators of severity are highlighted based on evidence supporting their causality in organ failure. Emphasis is placed on clinically relevant end points of organ failure and the mechanisms underlying the pathophysiological perturbations, which offer insight into potential therapeutic targets to treat.

Research Progress on the Relationship Between Acute Pancreatitis and Calcium Overload in Acinar Cells

Acute pancreatitis is a human disease with multiple causes that leads to autodigestion of the pancreas. There is sufficient evidence to support the key role of sustained increase in cytosolic calcium concentrations in the early pathogenesis of the disease. To clarify the mechanism of maintaining calcium homeostasis in the cell and pathological processes caused by calcium overload would help to research directly targeted therapeutic agents. We will specifically review the following: intracellular calcium homeostasis and regulation, the occurrence of calcium overload in acinar cells, the role of calcium overload in the pathogenesis of AP, the treatment strategy proposed for calcium overload.

The Potential Role of Dietary Platelet-Activating Factor Inhibitors in Cancer Prevention and Treatment

Cancer is the second leading cause of mortality worldwide. The role of unresolved inflammation in cancer progression and metastasis is well established. Platelet-activating factor (PAF) is a key proinflammatory mediator in the initiation and progression of cancer. Evidence suggests that PAF is integral to suppression of the immune system and promotion of metastasis and tumor growth by altering local angiogenic and cytokine networks. Interactions between PAF and its receptor may have a role in various digestive, skin, and hormone-dependent cancers. Diet plays a critical role in the prevention of cancer and its treatment. Research indicates that the Mediterranean diet may reduce the incidence of several cancers in which dietary PAF inhibitors have a role. Dietary PAF inhibitors such as polar lipids have demonstrated inhibitory effects against the physiological actions of PAF in cancer and other chronic inflammatory conditions in vitro and in vivo. In addition, experimental models of radiotherapy and chemotherapy demonstrate that inhibition of PAF as adjuvant therapy may lead to more favorable outcomes. Although promising, there is limited evidence on the potential benefits of dietary PAF inhibitors on cancer prevention or treatment. Therefore, further extensive research is required to assess the effects of various dietary factors and PAF inhibitors and to elucidate the mechanisms in prevention of cancer progression and metastasis at a molecular level.

Inflammation, not Cholesterol, Is a Cause of Chronic Disease

Since the Seven Countries Study, dietary cholesterol and the levels of serum cholesterol in relation to the development of chronic diseases have been somewhat demonised. However, the principles of the Mediterranean diet and relevant data linked to the examples of people living in the five blue zones demonstrate that the key to longevity and the prevention of chronic disease development is not the reduction of dietary or serum cholesterol but the control of systemic inflammation. In this review, we present all the relevant data that supports the view that it is inflammation induced by several factors, such as platelet-activating factor (PAF), that leads to the onset of cardiovascular diseases (CVD) rather than serum cholesterol. The key to reducing the incidence of CVD is to control the activities of PAF and other inflammatory mediators via diet, exercise, and healthy lifestyle choices. The relevant studies and data supporting these views are discussed in this review.

Phytoceuticals in Acute Pancreatitis: Targeting the Balance between Apoptosis and Necrosis

Despite recent advances in understanding the complex pathogenesis of pancreatitis, the management of the disease remains suboptimal. The use of phytoceuticals (plant-derived pleiotropic multitarget molecules) represents a new research trend in pancreatology. The purpose of this review is to discuss the phytoceuticals with pancreatoprotective potential in acute pancreatitis and whose efficacy is based, at least in part, on their capacity to modulate the acinar cell death. The phytochemicals selected, belonging to such diverse classes as polyphenols, flavonoids, lignans, anthraquinones, sesquiterpene lactones, nitriles, and alkaloids, target the balance between apoptosis and necrosis. Activation of apoptosis via various mechanisms (e.g., inhibition of X-linked inhibitor of apoptosis proteins by embelin, upregulation of FasL gene expression by resveratrol) and/or inhibition of necrosis seem to represent the essential key for decreasing the severity of the disease. Apart from targeting the apoptosis/necrosis balance, the phytochemicals displayed other specific protective activities: inhibition of inflammasome (e.g., rutin), suppression of neutrophil infiltration (e.g., ligustrazine, resveratrol), and antioxidant activity. Even though many of the selected phytoceuticals represent a promising therapeutic alternative, there is a shortage of human evidence, and further studies are required to provide solid basis to justify their use in the treatment of pancreatitis.

The regulatory effect of oxymatrine on the TLR4/MyD88/NF-κB signaling pathway in lipopolysaccharide-induced MS1 cells

BACKGROUND

Oxymatrine (OM), a major quinolizidine alkaloid extracted from the roots of Sophora flavescens, has been proved to regulate a variety of signaling pathways to produce a wide range of pharmacological effects.

OBJECTIVES

The regulatory effects of OM on the TLR4/MyD88/NF-κB signaling pathway under the stimulation of lipopolysaccharide (LPS) in MS1 cells were explored to illuminate the potential anti-inflammatory mechanism of OM for pancreatitis treatment.

METHODS

The signaling molecules related to the TLR4/MyD88/NF-κB pathway in MS1 cells were detected by Western blotting under different conditions, including OM pretreatment and LPS stimulation. The mRNA expression levels of TLR4, MyD88, NF-κB p65 and IκBα were detected by real-time PCR. The NF-κB p65 nuclear translocation in MS1 cells was measured by immunofluorescence, and the pro-inflammatory cytokine of IL-1β was detected by ELISA.

RESULTS

Increased levels of TLR4, MyD88 and NF-κB p65, induced by LPS stimulation, were significantly inhibited by OM pretreatment in MS1 cells. The decreased protein, but not mRNA, level of IκBα induced by LPS stimulation was increased by OM pretreatment. Meanwhile, LPS induced NF-κB p65 protein translocation to the nucleus as well as LPS increased expression of IL-1β were also inhibited by OM pretreatment.

CONCLUSION

Inhibitory effects of OM on molecules related to the TLR4/MyD88/NF-κB signaling pathway in pancreatic microvascular endothelial cells can alleviate inflammatory responses.

Hypoxia and hyperoxia potentiate PAF receptor-mediated effects in newborn ovine pulmonary arterial smooth muscle cells: significance in oxygen therapy of PPHN

Platelet-activating factor (PAF) acting via its receptor (PAFR) is implicated in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN). Effects of long-term oxygen therapy on newborn lung are not well understood; therefore, we studied the effect of oxygen tension on ovine newborn pulmonary artery smooth muscle cells (NBPASMC). Our global hypothesis is that PPHN results from failure of newborn lamb pulmonary system to downregulate PAFR activity or to upregulate vasodilatory cyclic nucleotides (Cnucs) activity. NBPASMC from newborns 6-12 days old were studied in vitro at three different oxygen tensions (pO2, [Torr]: hypoxia, <40; normoxia, 80-100; and hyperoxia, >100 Torr often clinically imposed upon newborns with PPHN) PAFR- and Cnucs mediated effects were determined. PAFR and PKA Cα mRNA expression as well as prostacyclin, thromboxane, cAMP production, and DNA synthesis was studied to assess PAFR-mediated hypertrophy and/or hyperplasia. Hypoxia and hyperoxia increased specific PAFR binding. PAF treatment during hyperoxia increased PAFR gene, but decreased PKA-Cα gene expression. Hypoxia and hyperoxia increased NBPASMC proliferation via PAFR signaling. Baseline prostacyclin level was ninefold greater than in fetal PASMC, whereas baseline thromboxane was sevenfold less suggesting greater postnatal cyclooxygenase activity in NBPASMC PAF decreased, while forskolin and 8-Br-cAMP increased cAMP production. Decrease of PAFR effects by Cnucs indicates that normal newborn PA physiology favors vasodilator pathways to minimize PAF-induced hypertrophy or hyperplasia. We speculate that failure of newborn lung to anchor downregulation of vasoconstrictors with upregulation of vasodilators leads to PPHN.

Current Understanding of Platelet-Activating Factor Signaling in Central Nervous System Diseases

Platelet-activating factor (PAF) is a bioactive lipid mediator which serves as a reciprocal messenger between the immune and nervous systems. PAF, a pluripotent inflammatory mediator, is extensively expressed in many cells and tissues and has either beneficial or detrimental effects on the progress of inflammation-related neuropathology. Its wide distribution and various biological functions initiate a cascade of physiological or pathophysiological responses during development or diseases. Current evidence indicates that excess PAF accumulation in CNS diseases exacerbates the inflammatory response and pathological consequences, while application of PAF inhibitors or PAFR antagonists by blocking this signaling pathway significantly reduces inflammation, protects cells, and improves the recovery of neural functions. In this review, we integrate the current findings of PAF signaling in CNS diseases and elucidate topics less appreciated but important on the role of PAF signaling in neurological diseases. We propose that the precise use of PAF inhibitors or PAFR antagonists that target the specific neural cells during the appropriate temporal window may constitute a potential therapy for CNS diseases.

Meta-analysis of effectiveness and safety of octreotide combined with alprostadil for acute pancreatitis

AIM: To systematically evaluate the effectiveness and safety of octreotide combined with alprostadil in the treatment of acute pancreatitis (AP).

METHODS: Relevant randomized controlled trials (RCTs) were searched via databases including PubMed, CBM, VIP, CNKI and WanFang Data from their inception to October 2015, and the references of the included studies were also screened. Two reviewers screened the literature, assessed the quality of studies and extracted the data. RevMan 5.2 software was used to complete the meta-analysis.

RESULTS: Eighteen trials involving 1277 participants were included. The results of the systematic review showed that compared with the control group, the experimental group was superior with regard to clinical effective rate (RR = 1.20, 95%CI: 1.15-1.26), time to relief of bellyache [SMD = -2.68, 95%CI: -3.11-(-2.25)], time to relief of signs of abdominal tenderness [SMD = -2.54, 95%CI: -2.79-(-2.30)], time to recovery of blood amylase [SMD = -1.95, 95%CI: -2.15-(-1.76)], incidence of AP complications (RR = 0.30, 95%CI: 0.13-0.69), and average length of hospital stay [SMD = -8.95, 95%CI: -13.61-(-4.29)].

CONCLUSION: Octreotide combined with alprostadil for treating AP is superior to octreotide alone. Due to the limited quality of the included studies, our conclusion needs to be verified by more high quality studies.

Biotinylated heptapeptides substituted with a D-amino acid as platelet-activating factor inhibitors

Platelet-activating factor (PAF), a potent lipid mediator, is implicated in many inflammatory diseases, and therefore may serve as a direct target for anti-inflammatory drugs. We previously reported that synthetic biotinylated peptides having a Tyr-Lys-Asp-Gly sequence markedly inhibit PAF-induced inflammation by direct binding, and that two synthetic fluorescence-labelled heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp and D-Lys-Trp-Tyr-Lys-Asp-Gly-Asp) with high stability in plasma specifically bind to PAF-like lipids (oxidized- and lyso-phosphatidylchoine). In this study, synthetic heptapeptides (Lys-Trp-Tyr-Lys-Asp-Gly-Asp) coupled to a biotin molecule through the N-terminal amino group and ε-amino group of N-terminus Lys, (Btn)KP6 and K(Btn)P6, respectively, and their biotinylated peptides substituted with D-Lys at the N-terminus, (Btn)dKP6 and dK(Btn)P6, respectively, were investigated for their effects on PAF-induced inflammation. In the experiments using a rat model of hind paw oedema, (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 significantly inhibited PAF-induced paw oedema, with the highest inhibitory effect exhibited by dK(Btn)P6. The inhibitory effect of D-Tyr-D-Lys-D-Asp-Gly tetrapeptide on PAF-induced paw oedema was much lower than that of Tyr-Lys-Asp-Gly tetrapeptide. In the experiments using tryptophan fluorescence spectroscopy, (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 bound to PAF dose-dependently, with dK(Btn)P6 showing the strongest binding affinity, indicating that its affinity appears to be closely correlated with its inhibitory effect on PAF-induced inflammation. These results suggest that direct binding of (Btn)KP6, K(Btn)P6, (Btn)dKP6, and dK(Btn)P6 to PAF can lead to marked inhibition of PAF-induced inflammation, and these agents, particularly dK(Btn)P6, may be useful as anti-inflammatory drugs targeting PAF with high stability in plasma.

Mechanism by which nuclear factor-kappa beta (NF-kB) regulates ovine fetal pulmonary vascular smooth muscle cell proliferation

Platelet activating factor (PAF) modulates ovine fetal pulmonary hemodynamic. PAF acts through its receptors (PAFR) in pulmonary vascular smooth muscle cells (PVSMC) to phosphorylate and induce nuclear translocation of NF-kB p65 leading to PVSMC proliferation. However, the interaction of NF-kB p65 and PAF in the nuclear domain to effect PVSMC cell growth is not clearly defined. We used siRNA-dependent translation initiation arrest to study a mechanism by which NF-kB p65 regulates PAF stimulation of PVSMC proliferation. Our hypotheses are: (a) PAF induces NF-kB p65 DNA binding and (b) NF-kB p65 siRNA attenuates PAF stimulation of PVSMC proliferation. For DNA binding, cells were fed 10 nM PAF with and without PAFR antagonists WEB 2170, CV 3988 or BN 52021 and incubated for 12 h. DNA binding was measured by specific ELISA. For NF-kB p65 siRNA effect, starved cells transfected with the siRNA were incubated for 24 h with and without 10 nM PAF. Cell proliferation was measured by DNA synthesis while expression of NF-kB p65 and PAFR protein was measured by Western blotting. In both studies, the effect of 10% FBS alone was used as the positive control. In general, PAF stimulated DNA binding which was inhibited by PAFR antagonists. siRNAs to NF-kB p65 and PAFR significantly attenuated cell proliferation compared to 10% FBS and PAF effect. Inclusion of PAF in siRNA-treated cells did not reverse inhibitory effect of NF-kB p65 siRNA on DNA synthesis. PAFR expression was inhibited in siRNA-treated cells. These data show that PAF-stimulation of PVSMC proliferation occurs via a PAFR-NF-kB p65 linked pathway.

Retroperitoneal abscess and acute acalculous cholecystitis after iatrogenic colon injury: report of a case

Acute acalculous cholecystitis has a high mortality rate due to the difficulties in early diagnosis and high rate of complications like empyema, gangrene and perforation. We report a case of 20-year-old male with acute severe pancreatitis, acute renal failure and acute peripancreatic fluid collection who was transferred to our department after blood filtration treatment in ICU. After percutaneous catheter drainage for 20 hours, the patient got a high fever. Computed tomography revealed retroperitoneal colon injury. In this case, percutaneous catheter drainage was performed again and the pus cavity was flushed regularly, after which the patient's state gradually improved. Unpredictably, septic shock appeared on the 51(st) day. Repeated computed tomography revealed acute acalculous cholecystitis and abscess formation. After percutaneous transhepatic gallbladder catheterization and drainage, the patient got better gradually. Three months later the retroperitoneal catheter was removed. Four months later, ultrasound examination showed normal gallbladder and the catheter was removed.

Platelet-activating factor (PAF)-antagonists of natural origin

Presently herbal medicines are being used by about 80% of the world population for primary health care as they stood the test of time for their safety, efficacy, cultural acceptability and lesser side effects. The discovery of platelet activating factor antagonists (PAF antagonists) during these decades are going on with different framework, but the researchers led their efficiency in studying in vitro test models. Since it is assumed that PAF play a central role in etiology of many diseases in humans such as asthma, neuronal damage, migraine, cardiac diseases, inflammatory, headache etc. Present days instinctively occurring PAF antagonist exists as a specific grade of therapeutic agents for the humans against these and different diseases either laid hold of immunological or non-immunological types. Ginkgolide, cedrol and many other natural PAF antagonists such as andrographolide, α-bulnesene, cinchonine, piperine, kadsurenone, different Piper species' natural products and marine origin plants extracts or even crude drugs having PAF antagonist properties are being used currently against different inflammatory pathologies. This review is an attempt to summarize the data on PAF and action of natural PAF antagonists on it, which were evaluated by in vivo and in vitro assays.

Synthetic biotinylated peptide compounds derived from Asp-hemolysin: novel potent inhibitors of platelet-activating factor

Platelet-activating factor (PAF: 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine), a potent inflammatory mediator, is implicated in many inflammatory diseases and may possibly serve as a direct target for anti-inflammatory drugs. We have previously reported that Asp-hemolysin-related synthetic peptides (P4-P29) inhibit the bioactivities of oxidized low-density lipoprotein (ox-LDL) containing PAF-like lipids by direct binding to ox-LDL, which plays a key role in the atherosclerotic inflammatory process. In this study, we investigated whether these peptides inhibit the bioactivities of PAF by binding to PAF and its metabolite/precursor lyso-PAF. In in vitro experiments, P21, one of the peptides, bound to both PAF and lyso-PAF in a dose-dependent manner and markedly inhibited PAF-induced apoptosis in human umbilical vein endothelial cells. Moreover, in in vivo experiments, P4 and P21, particularly their N-terminally biotinylated peptide compounds (BP4 and BP21), inhibited PAF-induced rat paw oedema dose dependently and markedly, and showed sufficient inhibition of the oedema even at doses 150-300 times less than the doses of PAF antagonists. These results provide evidence that direct binding of N-terminally biotinylated peptide compounds derived from Asp-hemolysin to PAF and lyso-PAF leads to a dramatic inhibition of the bioactivities of PAF, both in vitro and in vivo, and strongly suggesting that these compounds may be useful as a novel type of anti-inflammatory drug for the treatment of several inflammatory diseases caused by PAF.

Treatment with low-molecular-weight heparin reduces blood levels of PAF and ET-1/NO in rats with severe acute pancreatitis and hyperlipemia

AIM: To investigate the effect of treatment with low-molecular-weight heparin (LMWH) on microcirculation dysfunction in rats with severe acute pancreatitis (SAP) and hyperlipemia.

METHODS: SD rats were fed a high-fat diet for four weeks to induce hyperlipemia and randomly divided into sham operation group, control group, and experimental group. The control group and experimental group were then used to induce SAP, while the sham operation group underwent a sham operation. At 0, 6, 12 and 18 h after SAP induction, the experimental group was subcutaneouly injected with LMWH, and the control group was injected with normal saline. The concentrations of PAF and ET-1/NO in the portal vein blood were measured, and pancreatic microcirculatory structure was observed by electron microscopy.

RESULTS: The concentrations of PAF and ET-1/NO in the experimental group (5.9250 mmol/L ± 0.6113 mmol/L, 3.5368 ± 0.26) were significantly lower than those in the control group (7.4059 mmol/L ± 0.4281 mmol/L, 4.1697 ± 0.08), but were significantly higher than those in the sham operation group (4.4950 mmol/L ± 0.2628 mmol/L, 2.5133 ± 0.20). In addition, treatment with LWMH improved pancreatic microcirculation.

CONCLUSION: Treatment with LMWH improves pancreatic microcirculation in rats with SAP and hyperlipemia.

Soluble angiogenic factors in patients with acute pancreatitis

BACKGROUND

Angiogenic factors are involved in the physiopathology of several inflammatory diseases and they probably play a role in the pathogenesis of acute pancreatitis (AP).

AIMS

To investigate if angiogenic factors are elevated in patients with AP, their relationship with severity and clinical evolution of AP, and their use as prognosis markers of AP.

METHODS

A case (25)-control (30) study was carried out. Patients with AP were classified according to severity (using Ranson and Glasgow scores) and according to their clinical evolution (taking into account the development of complications during hospital stay). Platelet-derived growth factor (PDGFBB), angiopoietin-1, angiopoietin-2 (Ang-2), angiopoietin tyrosine-kinase receptor, hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), VEGF tyrosine-kinase receptor 1, and VEGF tyrosine-kinase receptor 2 were determined at 12 hours and then at 5 days after hospitalization.

RESULTS

PDGFBB, Ang-2, angiopoietin tyrosine-kinase receptor, and HGF were significantly higher in cases (P<0.001), and in patients with unfavorable clinical evolution (P<0.001). PDGFBB and HGF were significantly higher in patients with severe AP (P<0.05). To predict unfavorable clinical evolution, PDGFBB, Ang-2, and HGF showed an area under receiver operating characteristic curve of 0.97.

CONCLUSIONS

PDGFBB and HGF are related to severity of AP. These factors along with Ang-2 are related to clinical evolution and are useful in predicting the development of several complications during hospital stay. Therefore, these angiogenic factors could be useful as prognosis markers of AP.

Mechanism and dose-effect of Ginkgolide B on severe acute pancreatitis of rats

AIM: To determine the optimal dosage and mechanism of Ginkgolide B (BN52021) on severe acute pancreatitis (SAP) of rats.

METHODS: Seventy male Wistar rats were randomly divided into seven groups (10 for each group). Sham-operation group (SO), SAP model group (SAP), dimethyl sulfoxide (DMSO) contrast group (DMSO), and groups treated with 2.5 mg/kg BN52021 (BN1), 5 mg/kg BN52021 (BN2), 10 mg/kg BN52021 (BN3), and 20 μg/kg Sandostatin (SS). The SAP model was established in Wistar rats by injecting 5% sodium taurocholate retrogradely into the common bilio-pancreatic duct. The rats of SO, DMSO and BN52021 were injected with 0.9% NaCl, 0.5% DMSO and BN52021 through femoral vein 15 min after the operation. The SS group was injected with Sandostatin subcutaneously. All rats were anaesthetized at 6 h after operation, and venous blood was collected to determine the levels of serum amylase and phospholipase A2 (PLA₂), and pancreas tissue was harvested and stained.

RESULTS: There was no significant difference between the SAP and DMSO groups in serum amylase level, PLA₂, ascites and pathologic score, but significant difference was found in SAP/DMSO groups compared with those in SO group (P < 0.05) and the levels of serum amylase, PLA₂, ascites, and pathologic score were lower in the BN1, BN2, BN3 and SS groups than in the SAP and DMSO groups (P < 0.05). However, among BN1, BN2, BN3 and SS groups, BN2 had the best effect in decreasing the levels of serum amylase and PLA₂ (P < 0.05). Expression of platelet activating factor (PAF) receptor (PAFR) mRNA and protein showed no significant difference between the SAP and DMSO groups, or among BN1, BN2, BN3 and SS groups, but there was remarkable difference between SAP/DMSO group and SO group (P < 0.05), and expression of PAFR mRNA and protein was higher in the BN1, BN2, BN3 and SS groups than in the SAP and DMSO groups (P < 0.05). PAFR expression was observed in the nucleus and cytoplasm of pancreatic islet cells in Wistar rats by immunohistochemistry.

CONCLUSION: By iv injection, 5 mg/kg of BN52021 is the optimal dosage for SAP rats. BN52021 may inhibit the interaction/binding of PAF with PAFR.

Effects of dexamethasone and Salvia miltiorrhizae on the small intestine and immune organs of rats with severe acute pancreatitis

To observe the protecting effects and mechanisms of Dexamethasone and Salviae miltiorrhizae on intestinal mucosa and immune organs (spleen, thymus and lymph node) in rats with severe acute pancreatitis (SAP). The rats were randomly divided into sham-operated, model control, Dexamethasone treated group and Salviae miltiorrhizae treated group. At 3, 6 and 12 h after operation, the mortality rate, pathological changes of intestinal mucosa and immune organs as well as the contents of serum PAF, IL-1 beta and sIL-2R were observed, respectively. The mortality rate and the contents of PAF (at 3 and 6 h), IL-1 beta (at all time points) and sIL-2R (at 3 and 6 h) as well as the pathological scores of thymus (at all time points) and spleen (at 3 h) in Dexamethasone treated group were significantly lower than those in model control groups (P < 0.05). The contents of PAF (at 3 and 12 h), IL-1 beta (at 6 and 12 h) and sIL-2R (at 3 and 6 h) as well as the pathological scores of thymus (at all time points) and spleen (at 3 and 12 h) in Salviae miltiorrhizae treated group were markedly lower than those in model control groups (P < 0.05). Since both Dexamethasone and Salvia miltiorrhizae can reduce the contents of serum PAF, sIL-2R and IL-1 beta, mitigate the pathological changes in the small intestine, spleen and thymus and reduce the mortality rate of SAP rats, they show good therapeutic effects on SAP rats.

Effect of platelet-activating factor antagonist WEB 2086 on microcirculatory disorders in acute experimental pancreatitis of graded severity

OBJECTIVES

Platelet-activating factor (PAF) is an important mediator of inflammation and postulated to be involved in the pathogenesis of acute pancreatitis. In this study, we evaluated the therapeutic effect of PAF antagonist WEB 2086 in acute experimental pancreatitis of graded severity in rats.

METHODS

According to a block design, 64 animals were randomly allocated to 8 groups. Severe necrotizing pancreatitis was induced by intraductal infusion of taurocholic acid (4%, 0.4 mL), and the combination of glycodeoxycholic acid (10 mmol/L, 1.0 mL/kg, intraductal infusion) and cerulein (5 microg/kg per hour, intravenous) was applied to induce intermediate pancreatitis, or cerulein alone (5 microg/kg per hour, intravenous) to establish edematous pancreatitis. WEB 2086 was given 15 minutes after beginning the induction of pancreatitis. Pancreatic microcirculation was analyzed in vivo with an epiluminescent microscope. Histopathology was evaluated by a validated score. Trypsinogen-activating peptide and serum amylase were analyzed sequentially.

RESULTS

WEB 2086 had no significant influence on the breakdown of microcirculation, leukocyte adherence, histopathological damage, and amylase levels in severe necrotizing pancreatitis, intermediate pancreatitis, and edematous pancreatitis. Only in intermediate pancreatitis was there a significant reduction of trypsinogen-activating peptide levels.

CONCLUSIONS

In our study, PAF antagonist WEB 2086 had no beneficial effect on microcirculation in acute experimental pancreatitis.

G[alpha]i2 and G[alpha]q expression change in pancreatic tissues and BN52021 effects in rats with severe acute pancreatitis

OBJECTIVE

To investigate change of G[alpha]i2, G[alpha]q mRNA, and their proteins in severe acute pancreatitis (SAP) and BN52021 effects.

METHODS

Rats were assigned into negative-controlled group (NC), SAP-modeled group (SAP), and BN52051-remedial group (BN). Each group was assigned into 6 subgroups at different time points. G[alpha]i2, G[alpha]q mRNA, and their proteins were determined.

RESULTS

In the SAP group, G[alpha]i2 at 12 and 24 hours and G[alpha]q at 1 and 6 hours were remarkably higher than those in the NC group; in the BN Group, G[alpha]i2 is not remarkably different from that in the SAP group, but G[alpha]q at 1 and 6 hours was lower than those in the SAP group (P < 0.01), and G[alpha]i2 at 12 hours was higher than that in the NC group (P < 0.05), but G[alpha]q was not remarkably different from that in the NC group; in the SAP group, G[alpha]i2 and G[alpha]q proteins were higher than those in the NC group (P < 0.05); in the BN group, G[alpha]i2 proteins at 6, 12, and 24 hours and G[alpha]q proteins were lower than those in the SAP group (P < 0.05), and G[alpha]i2 and G[alpha]q proteins at each time phase point except 24 hours were higher than those in the NC group (P < 0.05).

CONCLUSIONS

G[alpha]i2, G[alpha]q mRNA, and their proteins in SAP increase. BN52021 decreases G[alpha]i2 and G[alpha]q.

Novel isoforms of intracellular platelet activating factor acetylhydrolase (PAFAH1b2) in human testis; encoded by alternatively spliced mRNAs

Platelet activating factor acetylhydrolase (paf-ah), a potent regulator of platelet activating factor activity, plays an important role in various physiological and pathophysiological functions including development, reproduction, inflammation, hemostasis, and apoptosis. Intracellular paf-ah (paf-ah-Ib) is composed of a regulatory subunit, Pafah1b1, and two highly conserved but non-identical catalytic subunits, Pafah1b2 and Pafah1b3. The present study identifies new splice variants of the Pafah1b2 gene transcript. The splice variants retain exons 1-5 and replace exon 6 with alternative exons derived from genomic sequence 3' to exon 6. Splice variants encode two proteins with different novel carboxy termini. One of the isoforms is expressed exclusively in testis. These new isoforms of pafah1b2 retain the ability to form higher order complexes while replacing known key catalytic residues, which raises the possibility that they may alter the subunit composition and catalytic function of paf-ah-Ib.

Significance of platelet activating factor receptor expression in pancreatic tissues of rats with severe acute pancreatitis and effects of BN52021

AIM: To investigate the dynamic changes and signi-ficance of platelet activating factor receptor (PAF-R) mRNA and protein in pancreatic tissues of rats with severe acute pancreatitis (SAP) and effects of BN52021 (Ginkgolide B).

METHODS: Wistar male rats were randomly assigned to the negative control group (NC group), SAP model group (SAP group), and BN52051-remedy group (BN group), and each of the groups was divided into 6 subgroups at different time points after operation (1 h, 2 h, 3 h, 6 h, 12 h, and 24 h) (n = 10 in each). PT-PCR and Western blot methods were used to detect PAF-RmRNA and protein expression in pancreatic tissues of rats respectively. Pathological examination of pancreatic tissues was performed and the serum amylase change was detected.

RESULTS: Serum amylase and pathological results showed the that SAP model was successfully prepared, BN52021 was able to decrease serum amylase, and the pathological ratings in BN group at 3 h, 6 h, and 12 h significantly decreased compared with those in the SAP group (8.85 ± 0.39 vs 5.95 ± 0.19, 9.15 ± 0.55 vs 5.55 ± 0.36, 10.10 ± 0.65 vs 6.72 ± 0.30, P < 0.05). The result of PAF-mRNA showed dynamic changes in SAP and BN groups, which increased gradually in early stage, reached a peak at 3 h (0.71 ± 0.14 vs 0.54 ± 0.14, 0.69 ± 0.13 vs 0.59 ± 0.04, P < 0.05), and decreased gradually later. There were significant differences at each time point except 1 h and 2 h, when compared with those in the NC group (0.71 ± 0.14 or 0.69 ± 0.13 vs 0.47 ± 0.10, 0.38 ± 0.08 or 0.59 ± 0.04 vs 0.47 ± 0.09, 0.25 ± 0.07 or 0.29 ± 0.05 vs 0.46 ± 0.10, 0.20 ± 0.06 or 0.20 ± 0.04 vs 0.43 ± 0.09, P < 0.05), whereas there was no significant difference between BN and SAP groups at each time point. The result of PAF-R protein showed that the change of PAF-R protein in the SAP group and the BN group was consistent with that of PAF-R mRNA. There were significant differences at each time point except 1 h, when compared with those in the NC group (0.90 ± 0.02 or 0.80 ± 0.05 vs 0.48 ± 0.02, 1.69 ± 0.06 or 1.58 ± 0.02 vs 0.48 ± 0.03, 1.12 ± 0.10 or 0.98 ± 0.03 vs 0.49 ± 0.09, 1.04 ± 0.14 or 0.87 ± 0.02 vs 0.52 ± 0.08, 0.97 ± 0.16 or 0.90 ± 0.05 vs 0.49 ± 0.10, P < 0.05), whereas there was no significant difference between the BN group and the SAP group.

CONCLUSION: PAF-R plays an important role in occurrence and development of SAP. BN52021 exerts biological effects through competitively inhibiting the binding of increased both PAF and PAF-R expression rather than through decreasing PAF-R expression in pancreatic tissues.

Why does pancreatic overstimulation cause pancreatitis?

Many animal models are available to investigate the pathogenesis of pancreatitis, an inflammatory disorder of the pancreas. However, the secretagogue hyperstimulation model of pancreatitis is the most commonly used. Animals infused with high doses of cholecystokinin (CCK) exhibit hyperamylasemia, pancreatic edema, and acinar cell injury, which closely mimic pancreatitis in humans. Intra-acinar zymogen activation is an essential early event in the pathogenesis of secretagogue-induced pancreatitis. Early in the course of pancreatitis, lysosomal hydrolases colocalize with digestive zymogens and activate them. These activated zymogens then cause acinar cell injury and necrosis, a characteristic of pancreatitis. Besides being the site of initiation of injury in pancreatitis, acinar cells also synthesize and release cytokines and chemokines very early in the course of pancreatitis, which then attract and activate inflammatory cells and initiate the disease's systemic phase.

Effect of BN52021 on NFκ-Bp65 expression in pancreatic tissues of rats with severe acute pancreatitis

AIM: To investigate dynamic changes and significance of expression of NF-κBp65 in pancreatic tissues of rats with severe acute pancreatitis (SAP), as well as BN52021 effects.

METHODS: Wistar male rats were randomly divided into negative control group (NC group, n = 60), SAP-model group (SAP group, n = 60), and BN52021-treated group (BN group, n = 60), and each of the above groups was respectively divided into 6 subgroups at different time points after operation (1 h, 2 h, 3 h, 6 h, 12 h, and 24 h) (n = 10). By RT-PCR and Western blot, NF-κBp65 mRNA and its protein expression in pancreatic tissues of rats were detected respectively.

RESULTS: The expression of NF-κBp65 mRNA dynamically changed in both SAP groups and BN groups. The mRNA level was higher in SAP groups than NC groups at 2 h, 3 h, 12 h, and 24 h after operation (P < 0.05), higher in BN groups than NC groups at all time points (P < 0.05), and higher in BN groups than SAP group at 1 h (P < 0.05). The NF-κBp65 protein level was higher in SAP groups than NC groups at 1 h, 3 h, and 6 h (P < 0.01), and 2 h, 12 h, and 24 h (P < 0.05), higher in BN groups than NC groups at all time points (P < 0.05), and lower in BN groups than SAP groups at 1 h, 3 h, and 6 h (P < 0.05).

CONCLUSION: The expression of NF-κBp65 in pancreatic tissues is dynamically changed and the changes play an important role in pathogenesis of SAP. BN52021 exerts therapeutic effects through reducing the expression level of NF-κBp65 protein in the early stage of SAP.

Experimental study of therapeutic efficacy of Baicalin in rats with severe acute pancreatitis

AIM: To observe the therapeutic efficacy of Baicalin in rats with severe acute pancreatitis (SAP) and explore its therapeutic mechanisms.

METHODS: The SAP rat models were randomly divided into the model control group, Baicalin treatment group, octreotide treatment group and sham operation group. All groups were randomly subdivided into 3 h, 6 h and 12 h groups with 15 rats in each group. The survival, ascites volume and pathological changes of pancreas in all rats were observed at different time points after operation. The plasma amylase content and serum TNF-α, IL-6, malonaldehyde (MDA) and PLA₂ contents were also determined.

RESULTS: The survival was not obviously different between the treated groups, and was significantly higher in treated groups at 12 h compared to the model control group (P < 0.05, 15 vs 10). The ascites/body weight ratio at 3 h and 6 h was significantly lower in Baicalin treatment group compared to the model control group and octreotide treatment group (P < 0.05, 1.00 vs 2.02 and 1.43 and P < 0.001, 2.29 (1.21) vs 2.70 (0.80) and 2.08 (2.21), respectively). The contents of amylase, TNF-α, IL-6, MDA and PLA₂ were significantly lower in the treated groups than in the model control group (P < 0.05, 4342 vs 5303, 5058 vs 6272 in amylase, P < 0.01, 21.90 vs 36.30, 23.80 vs 39.70, 36 vs 54.35 in MDA and 56.25 vs 76.10 in PlA₂, or P < 0.001, 65.10 and 47.60 vs 92.15 in TNF-α, 3.03 vs 5.44, 2.88 vs 6.82, 2.83 vs 5.36 in IL-6, respectively). The pathological scores of pancreas in the treated groups were significantly lower than that in the model control group (P < 0.05, 9.00 vs 10.05, 6.00 vs 9.00, 8.00 vs 10.05), but no marked difference was found between the treated groups.

CONCLUSION: The Baicalin injection has significant therapeutic effects on SAP rats, its effects are similar to those of octreotide. The Baicalin injection is also cheap and has a big application range, quite hopefully to be used in clinical treatment of SAP.

Novel iso-branched ether lipids as specific markers of developmental sporulation in the myxobacterium Myxococcus xanthus

Iso-fatty acids (FAs) are the dominant FA family in all myxobacteria analyzed. Furthermore, it was postulated that iso-FAs or compounds derived thereof are involved in fruiting body formation in Myxococcus xanthus, since mutants with a reduced level of iso-FA due to a reduced level of the precursor isovaleryl-CoA, are delayed in aggregation and produce only few myxospores. To elucidate the function of iso-FAs and their corresponding lipids we have analyzed the developmental phenotype of mutants having different levels of iso-FAs resulting in a clear correlation between the amount of iso-FAs and the delay of aggregation and reduction in spore yield. Addition of either isovalerate or 13-methyltetradecanoic acid resulted in restoration of the wild-type FA profile and normal development. Detailed analysis of the fatty acid (FA) profile during fruiting body formation in Myxococcus xanthus wild-type revealed the specific accumulation of 13-methyltetradecanal and 1-O-13-methyltetradecylglycerol which were produced specifically in the myxospores and which are derived from 1-O-(13-methyl-1-Z-tetradecenyl)-2-O-(13-methyltetradecanoyl)-glycero-3-phosphatidylethanolamine (VEPE) and 1,2-di-(13-methyltetradecanoyl)-3-(13-methyltetradecyl)glycerol (TG-1), respectively. The structures of these unusual ether lipids have been determined by spectrometric methods and synthesis (for TG-1). Analysis of several mutants blocked at different stages of development indicated that the biosynthesis of TG-1 is developmentally regulated and that VEPE might be an intermediate in the TG-1 biosynthesis. Finally, addition of TG-1 to mutants blocked in the biosynthesis of isovaleryl-CoA could restore aggregation and sporulation emphasizing the important role of iso-branched lipids for myxobacterial development.

Control of phospholipase A2 activities for the treatment of inflammatory conditions

Phospholipase-A2 (PLA2) enzymes hydrolyze cell membrane phospholipids to produce arachidonic acid (AA) and lyso-phospholipids (LysoPL), playing a key role in the production of inflammatory lipid mediators, mainly eicosanoids. They are therefore considered pro-inflammatory enzymes and their inhibition has long been recognized as a desirable therapeutic target. However, attempts to develop suitable PLA2 inhibitors for the treatment of inflammatory diseases have yet to succeed. This is due to their functional and structural diversity, and their homeostatic and even anti-inflammatory roles in certain circumstances. In the present review we outline the diversity and functions of PLA2 isoforms, and their interplay in the induction and inhibition of inflammatory processes, with emphasis on discussing approaches for therapeutic manipulation of PLA2 activities.